An Unexpected 2,3-Dihydrofuran Derivative Ring Opening Initiated by Electrophilic Bromination: Scope and Mechanistic Study

2014 ◽  
Vol 80 (1) ◽  
pp. 453-459 ◽  
Author(s):  
Yi Zhao ◽  
Ying-Chieh Wong ◽  
Ying-Yeung Yeung
Keyword(s):  
Ring Opening ◽  
Mechanistic Study ◽  
Electrophilic Bromination

Cationic Ring-Opening Polymerization of Trimethylene Urethane:  A Mechanistic Study

1997 ◽  
Vol 30 (5) ◽  
pp. 1289-1297 ◽  
Author(s):  
Stephan Neffgen ◽  
Helmut Keul ◽  
Hartwig Höcker
Keyword(s):  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Mechanistic Study ◽  
Cationic Ring Opening Polymerization

Mechanistic Study of Bu2SnCl2-Mediated Ring-Opening Polymerization ofɛ-Caprolactone by Multinuclear NMR Spectroscopy

2003 ◽  
Vol 9 (18) ◽  
pp. 4346-4352 ◽  
Author(s):  
Gaëlle Deshayes ◽  
Frédéric A. G. Mercier ◽  
Philippe Degée ◽  
Ingrid Verbruggen ◽  
Monique Biesemans ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Mechanistic Study ◽  
Multinuclear Nmr ◽  
Multinuclear Nmr Spectroscopy

Cationic ring-opening polymerization of cyclic carbonates and lactones by group 4 metallocenes: A theoretical study on mechanism and ring-strain effects

2017 ◽  
Vol 16 (01) ◽  
pp. 1750003 ◽  
Author(s):  
Jitrayut Jitonnom ◽  
Wijitra Meelua
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Bond Cleavage ◽  
Mechanistic Study ◽  
Chain Growth ◽  
Ring Size ◽  
Cyclic Carbonates ◽  
Complex Catalyst ◽  
Ring Strain ◽  
Group 4

Group 4 metallocene-mediated cationic ring-opening polymerizations of a series of lactones and cyclic carbonates, with different ring sizes ([Formula: see text]–8) have been theoretically studied. Using the “naked cation” approach in combination with density functional theory, the activated chain-end mechanism and the influence of transition metals, solvent and monomer ring size on the polymerizability were explored in detail. The results showed that the cationic metallocene–monomer complex, [catalyst][monomer][Formula: see text], is formed, generating cationic (carbocation ion) species responsible for polymer chain growth. We found that poor polymerizability of five-membered lactone and six-membered ring carbonate depends not only on the nature of the monomer ring size but also the relative stability of the complex, which was found to correlate well with the ring strain. Subsequently, several propagation steps take place through an SN2 reaction which involves ring opening of an active monomer, via alkyl–oxygen bond cleavage. Based on the computed activation energies of all metallocene systems, the first propagation was found to be the rate-determining step of the overall propagation and the hafnocene was found to be most active with the energy barrier of 17.6[Formula: see text]kcal/mol, followed by zirconocene (18.6[Formula: see text]kcal/mol) and titanocene (19.5[Formula: see text]kcal/mol), respectively. The mechanistic study may be applicable to the cationic ROP of lactides and other related monomers.

Anionic Ring-Opening Polymerization of Hexafluoropropylene Oxide Using Alkali Metal Fluorides as Catalysts: A Mechanistic Study

2009 ◽  
Vol 42 (3) ◽  
pp. 612-619 ◽  
Author(s):  
Sergei V. Kostjuk ◽  
Esteban Ortega ◽  
François Ganachaud ◽  
Bruno Améduri ◽  
Bernard Boutevin
Keyword(s):  
Alkali Metal ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Mechanistic Study ◽  
Metal Fluorides ◽  
Hexafluoropropylene Oxide ◽  
Anionic Ring
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